α-Cyanation of Aromatic Tertiary Amines using Ferricyanide as a Non-Toxic Cyanide Source

The reaction of aromatic tertiary amines with potassium ferricyanide directly provides the useful α‐amino nitriles. The inexpensive iron complex functions both as an oxidant and as a cyanide source. The presence of molecular oxygen speeds up the reaction which can be performed in aqueous tert‐butanol or even in ethanol‐based mixtures like Tequila. While amine cyanations usually employ highly toxic cyanide sources, potassium ferricyanide is even less toxic than table salt. No expensive metal complexes are required as catalysts and the co‐product of the cyanation, Prussian blue, has no known toxicity and is rather used as an antidote.